1. Field of the Invention
The present invention relates to a measuring instrument for checking the functional capability of an electric heating wire of a surface heating system before it is installed and for indicating damage to the heating wire while it is being installed, comprising a power supply, connecting devices electrically connected to the power supply and to which the free ends of an electric heating wire can be connected such as to form a current circuit on the power supply, a resistance measuring device which is designed to record the electric resistance of a heating wire connected to the power supply, and a display device which displays an electric resistance of a heating wire recorded by the resistance measuring device. Furthermore, the present invention relates to a method for checking the functional capability of an electric heating wire of a surface heating system before it is installed and for indicating damage to the heating wire while the latter is being installed by using this type of measuring instrument.
2. Description of the Related Art
Electric surface heating systems are known from the prior art in a wide variety of configurations. They comprise at least one heating wire that can be incorporated into a heating mat by the manufacturer. The heating wire is normally installed in a mortar or thin bed mortar layer disposed immediately beneath the floor covering during installation, and for this reason very fast response times can be achieved by the heating. Another advantage of electric surface heating systems is that they mostly have a very low structure, and for this reason they can be retrofitted with very little effort, for example within the framework of the renovation of an old building or the like.
One basic prerequisite for the correct operation of an electric surface heating system is that the heating wire used functions correctly, i.e. it is not damaged. Since the subsequent replacement of a heating wire is associated with a lot of effort and high costs due to it being embedded in said mortar layer, it is recommended to check the correct function of the heating wire before installing it. In addition, the functional capability of the heating wire should also be monitored during installation in order to ensure that the heating wire is not inadvertently damaged while being installed.
In order to check the correct functioning of a heating wire a commercially availably continuous tester that measures the electric resistance of the heating wire can in principle be used. If the electric resistance of the heating wire comes within a previously defined target value range, correct function is guaranteed. A commercially available continuous tester comprises a power supply, connecting devices connected electrically to the power supply and to which the free ends of an electric heating wire can be connected such as to form a current circuit on the power supply, a resistance measuring device which is designed to record the electric resistance of a heating wire connected to the power supply, and a display device which displays an electric resistance of a heating wire recorded by the resistance measuring device. However, a problem associated with commercially available continuous testers is that their handling is very confusing for a layman. This is due to the fact that commercially available continuous testers have a plurality of setting options in order to guarantee the most flexible possible applicability to a wide variety of technical domains. Another disadvantage of commercially available continuous testers is that, if the continuous tester is used to monitor the functional capability of a heating wire while it is being installed, the display device must be constantly observed by an installer so that, if the heating wire is damaged, he can quickly determine the associated decrease in electric resistance.